Mendenhall, Pa.— At dusk on Tuesday, as the sun sets over the Philadelphia suburbs, Eric Fehrnstrom, Mitt Romney’s senior adviser, steps off of the campaign’s dark-blue bus. His head is down, his hair mussed. As he strolls to the nearby ballroom where Romney will soon speak, his fingers work the keypad of his cell phone. A few hours earlier, Rick Santorum, Romney’s chief rival, suspended his campaign, making Fehrnstrom’s longtime boss the presumptive Republican nominee. But Fehrnstrom isn’t celebrating. In fact, Romney’s entire entourage, the political aides and advance staffers, are pretty much stone-faced and workmanlike. In many respects, from operations to strategy, they shifted to a general-election mindset weeks ago. The Santorum announcement merely made it official.

Backstage, Romney shakes hands with Chester County Republicans near a large bowl of Caesar salad and a pile of miniature hot dogs. Cameras flash. The former Massachusetts governor, in a dark suit and aqua-green tie, poses for pictures. He’s upbeat and smiling. Fehrnstrom, looking on, tells me that the campaign will now, finally, focus its full firepower on the White House. “Our goal, from the very first day Governor Romney got into this race, was to get into a one-on-one contest with the president,” he says. “We have arrived at that point. We will work to accumulate delegates, which continues to be important. But we are very much turning our attention to the imperative of defeating President Obama.”

Around the Beltway, the conventional wisdom, even among sympathetic Republicans, is that Romney arrives a bit late to the general election, and has been bruised by the primary battle. Much has been made about the president’s head start, in terms of fundraising and national organizing. Fehrnstrom shrugs off the anxious chatter. The drawn-out primary made Romney a “better candidate,” he insists. “He had worthy competitors, as many as eight of them who were vying for the nomination at one time. He participated in 20 debates. I think that has tempered him and made him into a stronger candidate.”

Among the hundred-plus local Republicans milling in the reception area here, 30 miles south off Independence Hall, the general sentiment is a 50-50 mix of Fehrnstrom’s optimism and wary skepticism. As I wander from table to table, I hear similar refrains. To all, Romney has been accepted, begrudgingly or warmly, as the nominee. That’s a given. The whispers about a white-horse hero in Tampa have long since faded from popular conversation. And rarely do I hear about Newt Gingrich and Representative Ron Paul. They’re candidates, not top-tier contenders.

Romney, for his part, has many admirers. Activists and donors respect his business background, his values, and his smarts. What Romney lacks, for the moment, are devotees, the kind of people who swoon over a pol. He has yet to prove to many conservative voters, even here in the affluent suburbs, that he can win in the fall — that he’s capable of carrying the party on his shoulders.

One of those skeptics, Colin Hanna, is standing by the salad bowl. Hanna, the president of Let Freedom Ring, a national conservative group, is confident that Romney can win southeastern Pennsylvania, a critical swing region dominated by moderate Republicans and independents, in the general election. What worries Hanna, a former Chester County commissioner, is Romney’s ability to excite the Right. His right-wing comrades, sipping drinks and talking politics, nod.

“A lot of people are still grieving our good senator’s withdrawal from the race,” Hanna says wistfully. “The real question is, will Romney reach out to conservatives in a meaningful way, or will he take us for granted?” He argues that Romney “missed an opportunity” early on to distance himself from the Bay State health-care program. Romney’s refusal to call the program a “mistake,” Hanna says, is a reason that many conservatives are reluctant to loudly cheer his ascendance.

Finding Hanna’s opposite, someone who is very much enthused by Romney’s rise, is easy. The local politicians, especially the congressmen who will share a ballot with Romney, are excited to have Romney on the top of the ticket. Representative Jim Gerlach, a Philadelphia-area Republican who has won many nail-biting races in a deeply purple district, predicts that Romney will help GOP candidates in suburban areas here and around the country. “We just did an internal poll a couple weeks ago in my district, and he’s beating President Obama right now by about five points,” he says. “I’m very comfortable with him, and that’s why I endorsed him back in November. His private-sector background fits places where the economy is the issue, and his record in Massachusetts, especially in working across party lines, is going to resonate. If he can win in this part of the state, he can win Pennsylvania, and that would mean a lot in November.”

Senator Pat Toomey, a freshman Republican, agrees with Gerlach. Toomey won statewide two years ago on a pro-business message, and Romney, he says, can do the same. “There are an awful lot of Democrats and independents in Pennsylvania who have conservative values, who are culturally conservative, in the broadest sense,” Toomey says. “There’s a commonsense conservatism, and they have seen a Democratic party that has veered way to the left, and that isn’t what they want. If we appeal to those voters and that basic common sense, we can carry a lot of those folks, as I did in 2010, and Governor Romney can carry the state.”

A few minutes later, as the well-dressed party types pack themselves into the ballroom, Toomey talks up Romney in his introductory speech. He praises Santorum, a “man many of us have known,” but takes care to remind the audience, especially the conservatives, that the time for internecine warfare is over, and that Romney has the “tenacity” to win. “I’ve studied his record very carefully, I’ve paid attention to this campaign,” Toomey says. He pauses and looks around the room. “I don’t think there is any question that he governed Massachusetts as a solidly fiscally conservative governor, in spite of having a very liberal legislature.” At that, the crowd applauds. It’s not a roar, but it’s a healthy applause, and Romney, standing aside, beams.

When he visited the Philadelphia suburbs last week, stumping ahead of the state’s April 24 primary, Romney was actively preparing for another brawl with Santorum. His campaign had purchased $2.9 million in television advertising space, preparing to launch an all-out air war. Then, on Tuesday morning, the governor received an “unexpected” call from Santorum, which effectively made him the party’s nominee, Fehrnstrom says. “This has been quite a day for me,” Romney says at the top of his remarks. “I kind of like today, I’ve got to be honest.” He spends the next 20 minutes talking about Obama and the economy. He too praises Santorum.

Beyond that, it’s a version of his usual stump speech. Across the country in Florida, President Obama is already firing away in a speech to college students. Up on stage, Romney crisply details his dissatisfaction with the president’s agenda, point by point. “The right course for America is not to divide America,” Romney says. “[Obama’s] campaign is all about finding Americans to blame and attack.”

The general election has arrived.

But for a minute, Romney, takes a brief sojourn from the script. “It’s a fun night,” he says. “We have work to do ahead of us, but let’s enjoy the night.” The audience murmurs its approval. As the glasses clink, Fehrnstrom and the rest of Romney’s advisers are already back near the bus, on their phones and laptops, looking ahead.